caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, cacao, and kola nuts and used medicinally as a stimulant and diuretic

Examples of caffeine in a Sentence

Her doctor told her to avoid caffeine.

Recent Examples on the Web

Matcha contains more caffeine and antioxidants than green tea and may have more pronounced health benefits. —Sarah Bence, Verywell Health, 1 Oct. 2025

How to treat norovirus While there is no specific treatment to treat the illness, the CDC recommends drinking lots of water or other drinks, like sports drinks, that don’t have caffeine or alcohol, which dehydrate you. —Miami Herald, 30 Sep. 2025

Coffee and tea count for regular caffeine consumers. —Dr. Jamin Brahmbhatt, CNN Money, 30 Sep. 2025

To take things up a notch, caffeine energizes dull, tired skin for an instant wake-up call. —Christa Joanna Lee, Allure, 30 Sep. 2025

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Phrases Containing caffeine

• caffeine-free

Rhymes for caffeine

• agin
• alkene
• allene
• ameen
• amin
• amine
• arene
• athene
• baleen
• beeline
• benzene
• between

Kids Definition

caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun

caf·​feine ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən 

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic

caffeinic

ka-ˈfē-nik  ˌkaf-ē-ˈin-ik 

adjective